Automatic total reducers monitoring and adjustment system

ABSTRACT

A process and apparatus for automatically monitoring or adjusting, or both, the concentration of total reducers (i.e. reduced sulfur-containing constituents which consume iodine) in an aqueous medium (e.g. waste water stream) whereby the time period for iodine titration of an untreated sample of the aqueous medium is automatically measured and this time measurement is automatically translated into an output signal to either a monitoring means or a process adjustment means (e.g. oxidant chemical feed pump) or both.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a process and apparatus for monitoringor adjusting, or both, the concentration of total reducers in a watermedium.

2. Brief Description of the Prior Art

Oil refineries and other industrial complexes often have effluent wastewater streams which contain high concentrations of reduced sulfurcompounds including sulfides (S⁻²), thiosulfates (S₂ O₃ ⁻²) and sulfites(SO₃ ⁻²). Such waste water streams must be chemically treated or placedin bioponds before being discharged into public waterways or going topublic owned treatment works in order to comply with discharge permits.One common method of treating these sulfur-bearing waste water streamsis by adding to the stream an oxidizing chemical such as hydrogenperoxide, chlorine dioxide, potassium permanganate, chlorine gas, sodiumhypochlorite or ozone.

In the past, the required amount of oxidizing chemical to be added tothe waste water stream was determined by first analyzing a batch sampleof the stream. This batch analysis was then related to the flow rate ofthe stream and the final treated pollutant level desired. The chemicaloxidant feed rate was manually adjusted following every suchdetermination.

The standard laboratory analysis for measuring the aggregateconcentration of reduced sulfur compounds was a batch iodometricanalysis. This analysis is sometimes referred to as a Total Reducersanalysis. Such an analysis attempts to determine the aggregateconcentration of all of the reduced sulfur compounds and other chemicalswhich consume iodine. One particular known batch method involves firstadding four chemical reagents (i.e. a pH 5.0-5.5 phosphate buffer, amethyl red indicator solution, hydrochloric acid and a starch indicatorsolution) to a waste water sample. Then, an iodine solution is titratedinto the mixture of the waste water sample and chemical reagents until acolor change occurs. The reduced sulfur components in the water samplequantitatively react with the iodine titrant under certain acidicconditions (i.e. pH 5.0-5.5). When all of these reduced species areconsumed by this reaction, the iodine starts to react with the starchindicator to form a blue complex signaling the end point of thetitration. Upon reaching the endpoint, the total amount of titratediodine is measured and the concentration of total reducers as milligramsof thiosulfate as sulfur or sulfite as sulfur per liter of water iscalculated therefrom.

Typical batch analysis procedures are illustrated in APHA StandardMethods 13th Edition, 1971, pages 337 and 338 and the Modified LosAngeles County Sanitation District Method September 1985 and Olin WaterServices Analytical Method for Total Reducers Titration (dated November1985). All three of these procedures are incorporated herein byreference in their entireties.

Until the present invention, no one had attempted to automate anystandard batch iodometric analysis so that the total reducers level in awaste water stream could be continuously monitored. Furthermore, noTotal Reducers analytical system has been used to automatically controlprocess adjustment means (e.g. oxidant chemical feed pumps).

Technicon Industrial Systems of Terrytown, New York, has manufactured anon-line hydrogen sulfide monitor (Model 650) for the intermittent (onceper hour) detection of hydrogen sulfide (H₂ S) content in an aqueousstream using a colorimetric methodology of detection. However, thisTechnicon monitor does not measure thiosulfate and other total reducerconstituents in an aqueous stream.

Dionex Corporation of Sunnyvale, Calif., manufactures an on-line monitor(Model 8000) which is capable of detecting the concentration of theindividual anion and cation components in an aqueous stream with ionexchange methodology. By this method, a small sample of a water streamis passed through an ion exchange column and the various ionicconstituents are loosely attached by the ionic charge to the resin.During regeneration of the resin column, the various ionic contituentsare eluted in a specific order and may be qualitatively identified andquantitatively measured by ion chromatography.

Both the Technicon and Dionex systems are very sensitive to the presenceof suspended solids and oils in the aqueous sample being tested.Accordingly, both use a submicron filter to pretreat the aqueous samplesbeing tested. This pretreatment of the sample may easily introduceerrors into the analysis procedure by removing a portion of the chemicalconstituents being analyzed. Accordingly, these Technicon and Dionexmonitors are best used for analyzing fresh water and laboratory water.Neither is well suited for waste water analysis. Finally, neithermonitor is designed to provide an output signal based on an monitoredcombination of a variable flow rate and a total reducers concentrationto a process control means (e.g. chemical feed pump) which controls thelevel of the oxidant reactant feed into a waste water stream.

Accordingly, there is a need in the water treatment industry for anautomated Total Reducers analytical system which can provide a veryfrequent analysis of total reducers concentration in a water streamwithout prefiltering or other preconditioning means. Furthermore, thereis a need in this industry for an automated Total Reducers analyticalsystem, when coupled with a flow monitoring means, that canautomatically control a process adjustment means (e.g. oxidant chemicalfeed pump), especially when a variable flow rate of water stream isinvolved. The present invention is a solution to both of these needs.

BRIEF SUMMARY OF THE INVENTION

The present invention, therefore, is directed to a process formonitoring or adjusting, or both, the concentration of total reducerconstituents in an aqueous medium, comprising the steps of:

(1) adding a predetermined aliquot of total reducers-containing water toa sample cell, said sample cell equipped with means for transmittinglight of variable intensities through the filled sample cell and meansfor sensing the presence or absence of said light transmission afterpassing through the filled sample cell;

(2) adding to said filled sample cell predetermined amounts of a pH5.0-5.5 buffer reagent, optional methyl red indicator, optionalhydrochloric acid and a starch indicator;

(3) activating said light transmission means in said sample cell inorder to send light of sufficient intensity to said light sensing meansthrough the filled sample cell;

(4) then titrating an iodine solution into the sample cell at apredetermined rate of addition while sensing the presence of said lighttransmission in said cell;

(5) measuring the time taken from the start of the iodine titrationuntil the absence of said light sensing through said filled cell isdetected;

(6) translating this time measurement into either the concentration oftotal reducer constituents in said water medium or into the amount of anoxidant chemical to be fed into said water medium or both; and

(7) based on said translation, sending either a first output signal toat least one monitoring means (e.g. a visual monitor, a printer or arecorder) or a second output signal to at least one process adjustmentmeans (e.g. an oxidant chemical feed pump) located on said water medium,whereby said concentration of total reducer constituents in said watermedium is adjusted, or sending both signals.

Furthermore, the present invention is directed to an apparatus formonitoring or adjusting, or both, the concentration of total reducerconstituents in a water medium; said apparatus comprising:

(a) a sample cell capable of containing a predetermined aliquot of atotal reducers-containing water sample and predetermined amounts ofchemical reagents and equipped with means for transmitting light ofvariable intensity through a filled sample cell and means for sensingthe presence or absence of light transmission through said filled cell;

(b) means for dispensing the predetermined aliquot of totalreducers-containing water into said sample cell;

(c) means for dispensing the predetermined amounts of chemical reagentsinto the sample cell, said chemical reagents comprising a pH 5.0-5.5buffer, optional methyl red indicator, optional hydrochloric acid and astarch indicator;

(d) means for titrating an iodine solution into said sample cell at apredetermined rate of addition until said light transmission is notsensed by light sensing means;

(e) means for measuring the period of time from the start of said iodinetitration to the point of detection of said absence of light sensing;and

(f) means for translating said time period into a determination ofeither the concentration of total reducer constituents in said watersample or into the amount of an oxidant chemical to be fed into saidwater medium, or both, and said translation means capable of providing afirst or second output signal or both signals based on said translation,said first output signal being sent to at least one monitoring means andsaid second output signal being sent to at least one process adjustmentmeans whereby the concentration of total reducer constituents in saidwater medium is adjusted.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 represents a diagrammatic outline of the flow of materials andelectrical output signals of a preferred embodiment of the presentinvention.

FIG. 2 is a detailed diagram of the dispensing means for the chemicalreagents in the preferred embodiment shown in FIG. 1.

FIG. 3 are diagrammatic top and side views of the optical liquid levelsensing system in the sample cell of the preferred embodiment of FIG. 1.

FIG. 4 are diagrammatic top and side views of the optical color changedetection system in the sample cell of the preferred embodiment of FIG.1.

DETAILED DESCRIPTION

The present invention will be described in view of the preferredembodiment shown in FIGS. 1, 2, 3 and 4. FIG. 1 shows differentcomponents of this preferred embodiment and how they interact.

I. WATER SAMPLE INTRODUCTION

On the left side of FIG. 1, a waste water stream 2 is shown. This wastewater stream contains reduced sulfur species (the aggregate thereof isknown and referred to herein as Total Reducers or T.R.). An untreatedsample of the stream 2 is drawn off at point 4 through sampling line 6and an open solenoid valve 8 to sample storage chamber 10. The chamberis preferably a cylinder about two feet in height and one or two inchesin diameter. The sample line 6 and sample chamber 10 are preferablyflushed with a fresh waste water sample before each analysis throughopen solenoid valve 12 and drain line 14 to the drain for a short periodof time (i.e. about 1 to 5 minutes) to insure that a representativefresh sample will be tested. The flow of the water sample throughsampling line 6, chamber 10 and drain line 14 is under the positivepressure of the waste water stream 2. At the end of this flushingperiod, solenoid valves 8 and 12 close and trap a water sample inchamber 10. In the next few minutes after these valves close, anyvolatile oil or light hydrocarbons in the trapped sample float to thetop of chamber 10 and any suspended solids drop to the bottom of chamber10. Next, solenoid valves 16 and 18 open. Solenoid valve 16, located atthe top of chamber 10, thus opens the chamber to the atmosphere throughvent line 20 to vent and to facilitate the gravity draining of chamber10. Solenoid valve 18 is located on line 22, which is a few inches abovethe bottom of the chamber 10. Thus, suspended solids in the sample willsettle below the location of the inlet to line 22. When solenoid valves16 and 18 are opened, the decanted water sample flows by gravity fromchamber 10 to a sample cell 24 through line 22. The size of samplestorage chamber 10 is relatively larger than the amount of the watersample to be sent to sample cell 24 and, accordingly, the volatile-richupper portion of the trapped water sample in chamber 10 is excluded fromthe transferred sample. This feature of the present invention thusminimizes the chances of fouling problems caused by the presence of oiland/or suspended solids that may be present in the water sample.

The amount of sample (preferably 100 ml of water sample) sent to samplecell 24 is controlled by an optical liquid level detector system shownin FIG. 3. The sample cell 24 is preferably made of clear acrylicplastic. Other similar clear, rigid and chemically inert materials maybe used instead for constructing cell 24. As the sample cell 24 fillswith the water sample from the bottom of the cell 24, it reaches thelevel of a light source 28 and light sensor 30. In an empty sample cell24, the path of light from light source 28 passes through air directlyto light sensor 30. When water reaches this level of the light path, thelight path is refracted by the water away from the sensor 30. Both ofthe effects are shown in FIG. 3. At that point of time, the sensor 30immediately sends an electronic signal to computer/interface module 32in an electronic enclosure shown in FIG. 1. The computer/interfacemodule 32 in turn sends an electronic signal to solenoid-activatedpiston 26 to close it, as it had previously done to open or close valves8, 12, 16 and 18 as described above. Power supply means 34 provides theelectric power for these signals. When solenoid-activated piston 26closes, a precise predetermined sample quantity has been introduced intosample cell 24 and is ready for testing.

II. CHEMICAL REAGENT DISPENSING

The next step is the dispensing of four initial chemical reagents intothe sample cell 24. These reagents are the same as used in theabove-described Olin Water Services Analytical Method and consist of thefollowing:

Reagent A. pH 5.0-5.5 phosphate buffer solution

(VWR Scientific AL14180-4)

Reagent B. Methyl Red Indicator Solution (Optional)

(Taylor Chemicals, Inc. R-1003F)

Reagent C. Hydrochloric Acid-6Normal (Optional)

(Hach Company #884-49)

Reagent D. Starch Indicator Solution

(Hach Company #349-37)

The reagent storage chamber 36 is shown in the upper right corner ofFIG. 1. In this storage chamber 36, the bulk containers of the reagentsA-D are stored as well as iodine titration solution (Reagent E) andcleaning solution storage container 38. The use of the latter twochemical solutions will be explained below. The bulk reagent containersA-E are connected to their corresponding reagent burets which are shownin detail in FIG. 2. The bulk storage containers A-E in chamber 36preferably contain bulk supplies of each Reagent A-E to allow for atleast 30 days of testing without the operator having to refill. Theburets and their connecting means to the sample cell 24 are not shown inFIG. 1.

Now referring to FIG. 2, the individual reagents A-E are introduced intoreagent holding burets 40, 42, 44, 46, 48, respectively, through topmanifold 50 which contains combination feed/drain lines 52, 54, 56, 58and 60. Located on each of these combination feed/drain lines are a pairof solenoid-activated pistons. Line 52 has fill pistons 62 and drainpiston 64. Line 54 has fill piston 66 and drain piston 68. Line 56 hasfill piston 70 and drain piston 72. Line 58 has fill piston 74 and drainpiston 76. Line 60 has fill piston 78 and drain piston 80.

The reagent burets are each attached through their bottoms into topmanifold 50. The combination feed/drain lines are machined channels intop manifold 50. Located adjacent to these machined channels is a sheetof flexible diaphragm material (not shown in FIG. 2). This diaphragmmaterial is sandwiched between this top channeled plastic plate havingthe feed/drain lines and a solid bottom plastic plate. The end of eachof the pistons is adhered to the diaphragm material and normally sealthe feed/drain channels by spring means. When a solenoid is activated bycomputer/interface module 32, the corresponding piston is drawn backinto the solenoid coil and the diaphragm in turn is drawn back to openthe channel. When the solenoid is deactivated for a piston, a returnspring on the piston is released and pushes the piston out of thesolenoid coil and thereby pushes the diaphragm into a channel and closesit. This stops the flow of that reagent.

Reagent burets 40, 42, 44, 46 and 48 are all standard glass tube typeburets. Preferably, burets 40, 42, 44 and 46 are identical in size (mostpreferably, a 0.25 inch inside diameter by 5.5 inches long). The buret48 is preferably larger (most preferably a 0.75 inch inside diameter by5.5 inches long). Of course, other buret diameters and lengths could beused and their preferred material of construction could be any othersimilar chemically inert and transparent material. The preferreddiaphragm material is a sheet of a terpolymer elastomer made fromethylene-propylene diene monomer (EPDM). Other suitable chemically inertand flexible materials may be used instead.

To illustrate the operation of this reagent dispensing system, note inFIG. 2 that Reagent A flows by gravity from its bulk container inreagent chamber 36 to buret 40 through fill line 52 whensolenoid-activated fill piston 62 is activated (opened) by an electronicsignal from computer/interface module 32. This flow fills buret 40upward from the bottom. The buret 40 is filled up to an upper opticalliquid level system consisting of a pinpoint light source 82 and lightsensor 84. This optical liquid level sensing system operates on the sameprincipal as the above-discussed sample cell filling optical system,that is, immediately upon reaching this light level, a signal is sent tocomputer/interface module 32, which immediately sends an electronicsignal to deactivate fill solenoid-activated piston 62 and thus closesthe fill line channel and thus cut off the flow of Reagent A into theburet 40.

After this filling operation is completed, a controlled amount ofReagent A is tranferred from buret 40 to sample cell 24 by gravitythrough drain line channel 52 by activating (opening) solenoid-activatedpiston 64. Whereas the sample water enters cell 24 through hole 112, theReagents A-E enter the cell from its open top which is in communicationwith the ends of the channels in top manifold 50. The amount of ReagentA sent to sample cell 24 is controlled by computer/interface module 32which sends electronic signals to piston 64 to open and close based on acalibrated time period. Reagents B, C and D are added sequentially totheir respective burets and then into sample cell 24 in the same manner.The preferred amounts and most preferred amount of each Reagent added tosample cell 24, when a 100 ml water sample having a pH between about 6and 8 is being tested, are as follows:

    ______________________________________                                                       Preferred   Most                                               Reagent        Amounts     Preferred Amount                                   ______________________________________                                        A.   pH 5.0-5.5    0.5-5.0   ml  1.0 ml                                            phosphate buffer                                                         B.   Methyl Red    0-0.4     ml  0.2 ml                                            Indicator                                                                C.   HCl-6 Normal  0-0.2     ml  0.1 ml                                       D.   Starch        0.75-2.0  ml  1.0 ml                                            Indicator                                                                     Solution                                                                 ______________________________________                                    

The time period which determines each reagent addition is calibratedperiodically (preferably, at least once per 24 hours) and is illustratedby the following procedure:

(i) Reagent A is filled into buret 40 to the level where the top lightsource 82 and light sensor 84 are;

(ii) Reagent A is then drained from buret 40 down to the lower opticalliquid level system consisting of light source 86 and light sensor 88;

(iii) The time required to go from the upper to lower optical liquidlevel systems in buret 40 is measured and then stored incomputer/interface module 32;

(iv) Since the volume of Reagent A between these two optical systems maybe predetermined, volume increments of this Reagent A can be sent tosample cell 24 by merely programming the desired dispensing time incomputer/interface module 32.

The amounts of the other Reagents B-E are calibrated in the same manner.

Before Reagents A, B, C and D are added to sample cell 24, a magneticstirrer motor 92 (shown in FIG. 2) below cell 24 is energized to rotatemagnetic stirrer bar 94 to provide agitation to the mixture of the watersample and Reagents. The stirrer bar 94 continues to rotate duringtitration of Reagent E into sample cell 24. The starting and stopping ofthe magnetic stirrer motor is controlled preferably by programmedcomputer sequencing in computer/interface module 32.

The Reagent autodispensing system, by using the above level sensingoptics and the computer/interface module 32, may be programmed toautomatically dispense each Reagent and self-calibrate itself to insureaccuracy in adding the correct amount of each Reagent to the sample cell24.

Furthermore, this autodispensing system does not employ peristalticpumps to transfer these Reagents into the sample cell 24. Peristalticpumps require frequent tubing changes (generally, at least monthly) toavoid leakage due to tubing wear. This continuous maintenance isexpensive and time-consuming and, if inadvertently neglected, may causeserious damage or expense to the process being treated. In contrast,with the autodispensing system of the present invention, corrosion andleaks are minimized or practically eliminated because the diaphragm isthe only moving part which the Reagents contact before they enter samplecell 24.

III. INITIAL LIGHT INTENSITY ADJUSTMENT

After the sample cell 24 has been filled with the water sample andReagents A, B, C and D and the resulting mixture agitated, a secondoptical system placed on the cell 24 is activated. This second opticssystem is shown in FIG. 4 and preferably consists of a controlled lightsource 96 and a light sensor 98. Controlled light source 96 ispreferably a red light-emitting diode having a light wavelength in therange of about 700 to 800 nanometers (nm).

The second optics systems is activated as follows: The light intensityof controlled light source 96 is gradually increased from zero intensityin increments by electronic signals from computer/interface module 32until light sensor 98 senses the presence of the red light from thesource 96 through the filled sample cell 24. At that point, sensor 98sends computer/interface module 32 an electronic signal and thecomputer/interface module 32 stops ramping up the light intensity. Thepurpose of this initial adjustment of light intensity is to null out theinterfering effects of sample color or turbidity which may vary fromwater sample to water sample.

IV. IODINE SOLUTION TITRATION

As soon as this light sensor 98 senses the light from source 96, anelectronic signal is sent through computer/interface module 32 whichactivates drain piston 80 in order to start titrating Reagent E (theiodine solution). The preferred standard iodine solution is 0.025 Normal(Taylor Chemicals Inc. #R-0635-40F). Simultaneously, thecomputer/interface module 32 activates an on board precise timemeasuring means (preferably accurate within a 1/100 of a second) tomeasure the time period from when the iodine titration begins until anabrupt change in light transmission is detected by this second opticssystem. In particular, as the iodine is added, it preferably is reactedor consumed with the total reducer constituents in the sample. Whenthese total reducers have completely reacted with the iodine solution,the starch indicator absorbs the excess iodine solution being titratedinto cell 24. At this point, the whole sample/reagent mixture turnscolor (e.g. from a red to a blue). This end point color change isregistered by the second optic system whereby light sensor 98 can nolonger sense the controlled light from source 96. The controlled lightbeam is now absorbed in the sample mixture rather than passing throughto sensor 98. When the end point is sensed, a signal is sent tocomputer/interface module 32 and solenoid-activated piston 80immediately stops the iodine titrant flow and stops the on boardelectronic time measuring means which was started when titrant flowstarted.

V. TRANSLATION OF RESULTS AND SIGNAL OUTPUTS

As stated above, the time required to reach this end point is measuredby the on board time measuring means in the computer/interface module32. This measured time period is translated into a concentration oftotal reducers in the sample. This is done in the computer/interfacemodule 32 by comparing the measured iodine titration time to thecalibrated time versus volume factor stored in the computer/interfacemodule 32 for buret 48. This comparison provides the total volume ofiodine solution consumed by the sample being tested. From thisdetermined iodine solution volume, the total reducers concentration inthe sample (if thiosulfate is the primary total reducer constituent) maybe calculated using the following Equation (A) which is stored in thecomputer/interface module 32: ##EQU1## where

A=millileter iodine titrant

N=normality of the iodine titrant

V=volume of sample (in ml)

64.12=2 times molecular weight of sulfur

Accordingly, if the normality of the iodine titrant is 0.025N and theamount of the sample used is 100 ml, then Equation (A) is: ##EQU2##

After the computer/interface module 32 has calculated this totalreducers concentration in the sample, the computer/interface module 32further calculates the amount of a particular oxidant chemical needed totreat the total reducers in the water medium from which the sample wasobtained. This calculation involved the following Equation (B): ##EQU3##The flow rate of the water medium may be continuously measured by a flowmonitor 100 which is attached to a water stream 2 at point 102 as shownin FIG. 1. The flow monitor 100 sends electronic signals (eitherintermittently or continuously) to computer/interface module 32. Thisflow rate signal is processed by the computer/interface module 32.Preferably, a continuous flow rate signal is received by thecomputer/interface module 32 from flow rate monitor 100. Thiscontinuously received (although possibly varying) input signals are usedby computer/interface module 32 to calculate the output adjustmentsignal to the oxidant feed pumps 104 and 106 in accordance with aboveEquation (B). One or more oxidant feed pumps may be controlled by thiscomputer output signal. The Reaction Ratio in the above Equation (B) isan empirical, programmable number dependent upon several factorsincluding the type of specific oxidant used; the individual totalreducer constituents present; type of oxidant; absence or presence of anoxidant catalyst; retention or reaction time; and starting concentrationversus the desired final concentration of total reducers in the watermedium. When copper sulfate catalyzed hydrogen peroxide is used as anoxidant, the main total reducer constituent is sodium thiosulfate,maximum retention time is about 0.75 hours and the concentration oftotal reducer concentration is desired to be lowered from about 200-400mg thiosulfate as sulfur per liter of sample down to a desired level ofless than 50 mg thiosulfate as sulfur per liter, this reaction rationumber programmed into computer/interface module 32 is is in the rangeof 1.5-2.5. However, the reaction ratio will vary with other oxidantsand the presence of other primary total reducer constituents and whereother ranges of starting and desired ending total reducer values areinvolved. Accordingly, the Reaction Ratio will vary from installation toinstallation and will have to be determined empirically in each case.

This calculated oxidant chemical amount to be added to the water mediumis translated by computer/interface module 32 into a pump adjustmentoutput signal which tells pumps 104 and 106 the quantity of oxidant tofeed into the water medium. This pump adjustment output signal ispreferably sent out from computer/interface module 32 to pumps 104 and106 on a continuous basis. Thus, the pumps will be constantly adjustingthe amount of oxidant chemical feed into waste water stream 2 inaccordance with similar changes in flow rate input. After each totalreducer sampling test, the total reducer value for Equation (B) will beupdated and the pump adjustment output signal will be based on this newtotal reducer value until the next sampling test.

Alternatively or simultaneously with this process adjustment function,the system of the present invention may be used to monitor the totalreducers concentration and, optionally, the flow rate in the watermedium, as well as the amount of oxidant to be added. This monitoringfunction may be carried out by sending electronic output signals to avideo monitor 108, printer 100 or a recorder (not shown in FIG. 1).Therefore, by this monitoring function, an operator may make a permanentrecord of the total reducers concentration in the water medium.Preferably, such monitoring means would log the flow rate information,the date and time of each Total Reducer analysis, the determined totalreducer value, as well as the magnitude of the pump adjustment outputsignal sent to each pump. Moreover, it is desirable thatcomputer/interface module 32 have the ability to store certainquantities of such data and having that stored data retrievable in bothvideo and printout form. Furthermore, the operator, by only using themonitoring function, may manually control oxidant feed pumps 104 and 106or additional standby pumps.

It should also be noted that if the water medium being sampled, andeither adjusted or simply monitored for total reducer values, or both,is a static body of water rather than a flowing stream, then Equation(B) will have to be changed. The volume of water being treated will haveto be used rather than the flow rate.

VI. WATER SAMPLE DRAINING

After the iodine titration is completed (i.e. color change end pointregistered), the agitation is stopped (i.e. the magnetic stirrer isturned off) and the liquid sample mixture is drained from sample cell 24through drain opening 112 (shown in FIGS. 2, 3 and 4). Sample cell 24 isalso preferably equipped with a vent opening 114 which facilitates thegravity draining of the cell. The draining system is best shown in FIG.2. After exiting through drain opening 112, the drained sample entersdrain channel 116 in bottom manifold 118 when solenoid-activated piston120 is activated (opened). This bottom manifold 118 is constructed in amanner similar to top manifold 50. The preferred material for thechanneled top plate and solid bottom plate of top manifolds 50 and 118is acrylic plastic like cell 24. The solenoid-activated piston 120 isadhered to a flexible diaphragm material so that when it is activated,it causes an opening in drain channel 116 in the bottom manifold 118.Then, the drained sample exits manifold 118 by drain line 122 into spentsample container 124 (as shown in FIG. 1).

VII. CELL CLEANING CYCLE

After the sample cell 24 has been drained, the cell is filled with acleaner solution made up of an appropriate hydrocarbon or halocarbonsolvent. The cleaner solution is used to remove any residue contaminants(e.g. oil films and remaining total reducers) in sample cell 24 so thatthe next testing will be accurate. The cleaner solution is stored incleaner reservoir 38 in reagent chamber 36. The cleaner solution flowsby gravity through feed line 126 through solenoid-activated piston 128into channel 116 in bottom manifold 118. It then enters sample cell 24through opening 112 and fills the cell 24 from the bottom. Piston 128 isautomatically opened as piston 120 is closed. A 150 ml aliquot ofcleaner solution is added and piston 128 is then closed. This amount ofcleaning solution added to sample cell 24 is controlled by the sameliquid leveling sensing system 28 and 30 used to add the sample water tothe cell 24. In this case, there is a time delay between when thecleaning solution level passes the leveling sensing system and whenpiston 128 is closed. If too much cleaner is added, the excess will exitsample cell 24 by exit vent 114 and overflow line 114A. After the cellis filled with cleaner, the magnetic stirrer motor 92 is energized tostart magnetic stirrer bar 94 to improve the cleaning action. Thecleaning operation lasts from about 1 to 5 minutes. The stirrer motor 92is stopped and the cleaning solution is drained by gravity from cell 24through drain opening 112, channel 116, and through piston 130, whichoperates in the same manner as the other solenoid-activated pistons.After passing by piston 130, the spent cleaner solution flows throughline 132 into spent cleaner container 134 (shown in FIG. 1). The spentcleaner solution may be recycled or discarded.

VIII. FLUSHING CYCLE

After the above cleaning cycle is completed, the sample cell is flushedwith sample water or fresh water through line 22, solenoid-activatedpiston 26, channel 116 into cell 24. Again, the liquid leveling system28 and 30 is used to obtain the desired amount of flush water. Themagnetic agitator mechanism restarts as described previously and flushwater is agitated in the cell 24 for a predetermined time interval (e.g.from about 1 to about 5 minutes) and then drained through channel 116and piston 120 back to the spent sample container 124.

The cell is ready for the next test cycle. Under normal operation, asample may be taken once per hour. If the output signal indicates anuncharacteristic high or low (outside a predetermined percentage ofchange) total concentration of total reducer constituents, the testingfrequency may be automatically increased (e.g. three times per hour)until the measured concentration appears stabilized.

IX. COMPUTER COMMAND SEQUENCE SUMMARY

Computer/interface module 32 is preferably made up of an eight BITcomputer (with a keyboard) which is in combination with an interfacemodule package capable of directing the computer commands to theindividual items (e.g. solenoids, solenoid-activated pistons, pumps andmagnetic agitator system) to be controlled in sequence. The preferredinterface module contains four computer programmable interface adapterintegrated circuits. These four integrated circuits route the computercommands to the electronic circuits and items that are to respond tothese commands. Of these four integrated circuits, one integratedcircuit preferably controls the solenoid-activated pistons that startand stop the liquid flow into and out of sample cell 24. The secondcontrols the liquid level in the reagent holding burets by responding tothe light sensors attached to these burets. The second also controls theliquid level in sample cell 24 by responding to the level sensor in thatsample cell. The third controls the milliamp level that is sent out tomodulate the chemical oxidant feed (e.g. process adjustment pumps) andthe intensity of the light source 96 used to determine titration time insample cell 24. The fourth integrated circuit controls the voltage levelwhich is compared to the flow monitor input milliamp signal and therelay drives for the solenoid valves which open and close the samplestorage chamber 10.

The computer/interface module 32 also preferably contains integratedcircuits and other means which convert digital electronic signals intoanalog electronic signals and vice versa.

The above described preferred embodiment of the process and apparatus ofthe present invention is directed by the following sequence of computeroperations:

1. The computer checks its internal day time clock and checks to see ifit is test time.

2. At test time the test sequence is started and performed as follows:

(a) Flush and capture a new test sample into the sample storage chamber10.

(b) Wait a predetermined programmed time period to allow for separationof suspended solids and oil in chamber 10.

(c) Fill the sample cell 24 with 100 mls of sample water from the samplestorage chamber 10.

(d) Turn on the magnet stirrer 94.

(e) Inject Reagents A-D into burets and then into cell 24.

(f) Set light intensity in light source 96 to compensate for color andturbidity.

(g) Inject iodine solution into buret 48 and then cell 24 by time/volumemeans until the color change end point is detected.

(h) Convert the time to titrate to volume of iodine used.

(i) Calculate the total reducer value.

(j) Measure the rate of flow in the waste water stream from the flowmonitor 100.

(k) Calculate the oxidant pump rate required based on total reducervalue calculated in (i), reaction ratio and measured water stream flowrate of (j).

(1) Send the pump setting output signal to the pumps 104 and 106corresponding to the calculated oxidant pump rate of (k).

(m) Drain the spent sample from the sample cell to the spent samplestorage container 124.

(n) Fill the sample cell 24 with up to 150 ml of cleaning solution.

(o) Agitate the cleaning solution for programmed time period to cleanthe sample cell for the next test.

(p) Drain the cleaning solution from the sample cell to the spentcleaner container 134.

(q) Fill sample cell 24 with up to 150 ml of fresh water or sample waterto flush cell 24 for next test

(r) Agitate flushing solution for programmed time period.

(s) Drain the flushing solution from the sample cell to spent samplecontainer 124.

(t) Print the time, date, total reducer value, pump rates and flow rateon the printer 110 and show on the video monitor 108.

3. While waiting for the next total reducers test, the computer 32continues to monitor the flow rate of the waste water stream and updatesthe pump setting output signal (1) above based on the last total reducervalue, predetermined reaction ratio and continuously measured flow rate.This pump setting output signal calculated in (u) above is continuouslysent to pumps 104 and 106 and the data in (t), above, is updated andprinted at printer 110 and video monitor 108.

What is claimed is:
 1. A process for monitoring or adjusting, orconcentration of total reducer constituents in an aqueous medium,comprising the steps of:(1) adding a predetermined aliquot of said totalreducers-containing water to a sample cell, said sample cell equippedwith means for transmitting light of variable intensity through thefilled sample cell and means for sensing the presence or absence of saidlight transmission after passing through said filled sample cell; (2)adding to said aliquot-filled sample cell predetermined amounts of a pH5.0-5.5 buffer reagent, an optional methyl red indicator, an optionalhydrochloric acid solution and a starch indicator; (3) activating saidlight transmission means in said sample cell in order to send light of asufficient intensity through said filled sample cell to be sensed bysaid light sensing means; (4) then titrating an iodine solution intosaid filled sample cell at a predetermined rate of addition whilesensing the presence or absence of said light transmission in said cell;(5) measuring the time taken from the start of the iodine titrationuntil the absence of said light sensing through said filled cell isdetected; (6) translating this time measurement into either theconcentration of total reducer constituents in said water medium or intothe amount of an oxidant chemical to be fed into said water medium, orboth; and (7) based on said translation, sending either a first outputsignal to at least one monitoring means or a second output signal to atleast one process adjustment means location whereby said concentrationof total reducer constituents in said water medium is adjusted, orsending both first and second signals.
 2. The process of claim 1 whereinsaid sample water has a pH of about 6 to about 8, for each 100 mlaliquot of sample water added to said sample cell, the following amountsof chemicals are added to said sample cell:

    ______________________________________                                        A.     pH 5.0-5.5 Phosphate Buffer                                                                       0.5-5.0  ml                                        B.     Methyl Red Indicator                                                                              0-0.4    ml                                        C.     HCl (6 Normal)      0-0.2    ml                                        D.     Starch Indicator Solution                                                                         0.75-2.0 ml                                        ______________________________________                                    


3. The process of claim 2 wherein said amount of chemicals added to saidsample cell are:

    ______________________________________                                        A. pH 5.0-5.5 Phosphate Buffer                                                                         1.0 ml                                               B. Methyl Red Indicator  0.2 ml                                               C. HCl (6 Normal)        0.1 ml                                               D. Starch Indicator Solution                                                                           1.0 ml                                               ______________________________________                                    


4. The process of claim 2 wherein the normality of the iodine titrant is0.025 Normal.
 5. The process of claim 1 wherein the concentration oftotal reducer constituents in said water medium is about 200 to about400 mg as sulfur (S⁼) per liter of water.
 6. The process of claim 5wherein said process adjustment means is an oxidant feed pump and asufficient amount of oxidant is added to said water medium to lower theconcentration of total reducers to below about 50 mg as sulfur (S⁼) perliter of water.
 7. The process of claim 1 wherein said sample cell iscleaned with a cleaning solution between each total reducer measurementtest.
 8. The process of claim 1 wherein said sample cell is flushed withfresh water or sample water between total reducer measurement tests. 9.The process of claim 1 wherein said first output signal is sent toeither a video monitor, a printer or both.
 10. The process of claim 1wherein said light transmission from said light transmission means tosaid light sensing means is at about 700 to about 800 nanometers.